Connecting Cables For The Cms - Siemens SIMATIC RF186C Operating Instructions Manual

5.6

Connecting cables for the CMs

Effect of cable length on the supply voltage
When wiring your assembly, you need to take into account the effect of the cable length on
the supply voltage of the communications module.
Observe the maximum supply currents
The maximum supply current of the communications module is 16 A at 1L+ and 2L+ for a
maximum ambient temperature of 40 °C. At ambient temperatures of 40 °C to 55 °C, the
maximum supply current is 12 A. These values must not be exceeded.
If you do not comply with the maximum supply currents and the required line cross-
sections, an increased supply current can lead to overheating of the cable insulation and
the contacts. This can result in damage to the communications module.
The following figure shows the voltage drop as a function of the cable length for 16 A, using
the example of a copper cable with ∅ 1.5 mm
Figure 5-12
To estimate the voltage drop in your communications module, you must add the voltage
drops of the cables.
SIMATIC RF185C, RF186C, RF188C, RF186CI, RF188CI
Operating Instructions, 06/2019, C79000-G8976-C512-02
CAUTION
Voltage drop with a cable cross-section of 1.5 mm
5.6 Connecting cables for the CMs
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Connection
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